Black Sludge

[john keefe]

Finally swapped a Bailey's alloy overflow tank in place of the plastic bottle, and noticed black sludge in the bottom of the plastic tank. Took a long time to polish it up, but looks great, although had to do some creative repositioning of the coil to get clearance.

Definitely not oil contamination, coolant is clear and looks good. No overheating, water pump is good and fairly new, etc.. Tank is a stock XR AL.

Not a lot of sludge, maybe a tablespoon total, but enough to bring up questions. Never had that before with the 5.0L. It's not rusty in color, its almost black. And, it's iron particles; I can pick it all up with a magnet.

So... I'm thinking its just slough-off from a 30 year old, albeit rebuilt 5.0L block that sat for a few months on jackstands for other work during this Covid, and is now "getting some action." Which is nice. When I rebuilt it, I didn't do a caustic tank flush as we used to do, since those have been illegal now around here for years. I'm guessing/hoping it's just a 30 year old block with some areas that thoroughly dried out due to inactivity which is now being sloughed off. Any ideas? Worst case scenario(s)?

[zxr250cc]

Hi all,

Was the motor sitting in an unheated area and not filled with coolant as I am guessing? Cooling and heating might have made it 'sweat' internally and cause some oxide creation (rust) that came loose when refilled with coolant. ?? Just a thought.

I personally never had problems like that with my Z600 Honda or old VW Beetles when in storage!

Cheers

[Ed Lijewski]

You said its iron particles...but hoses deteriorate from acidic conditions and slough off black material.

YMMV

[john keefe]

No, nothing special done before getting it up on jackstands... I only intended to have it up for a bit so I could work on some stuff, and prep for installing an hydraulic e-brake. Expected to run it during the Summer, but then a backlog of honey-do remodel projects got in the way.

Ed, thought it might be hose deteriorating, or some old radiator stop-leak stuff from before the engine swap, but all the hoses are fairly new, and a magnet picks all of it up. So, does have iron content.

[thesameguy]

Possible ir's pieces of water pump getting ground off?

[john keefe]

Water pump is worth a check, but it was new when I installed for the swap, and that's probably been less than 5K miles. No magnetic pick-up waving a wand in the coolant in the reservoir, though.